A New Method of Determining Payment for In-Place Concrete With Double-Bounded Compressive Strength Pay Factors

Details

• Creators:
  Sullivan, James L. ; Novak, David C. ; Hernandez, Eric M.
• Corporate Creators:
  University of Maine. Transportation Infrastructure Durability Center (TIDC)
• Corporate Contributors:
  United States. Department of Transportation. University Transportation Centers (UTC) Program ; United States. Department of Transportation. Office of the Assistant Secretary for Research and Technology
• Subject/TRT Terms:
  Cast In Place Concrete Compressive Strength Concrete Compressive Strength (CCS) Construction Projects Cracking Decision Support Systems Implementation Literature Reviews Payment Percent-within-distribution (PWD) Percent-Within-Limits (PWL) Performance Performance Based Specifications Probability Density Functions Quality Assurance Quality Control Random Variables Recommendations Risk Management Specifications Strength Of Materials

  More +
• Resource Type:
  Tech Report
• Geographical Coverage:
  United States
• Edition:
  Final Report
• Corporate Publisher:
  University of Maine. Transportation Infrastructure Durability Center (TIDC)
• Abstract:
  The Vermont Agency of Transportation currently uses a lower acceptance limit on 28-day concrete compressive strength (CCS) of 4,000 psi for acceptance of in-place concrete in its construction projects, particularly for placement of bridge decks. Over time, to reduce risk, the concrete industry’s response has led to increasingly higher average 28-day CCS, which is believed to be associated with increased brittleness and excessive early cracking. These findings have led to a recommendation to establish a target mean CCS of around 5,000 psi with pay factors and they support the argument for including an upper acceptance limit when CCS is used as a performance characteristic. Under this type of performance specification, pay factors are typically enforced for payment using the percent-within-limits (PWL) quality measure. A drawback of the PWL is its implicit assumption that the distribution of 28-day CCS is Gaussian so that z-scores can be used for assessment of payment. Our research team’s review of the literature and historical data suggests that the distribution of resulting industry-wide CCS is not likely to be Gaussian, especially once the double-bounded acceptance range is implemented. The goal of this project was to develop a new quality measure for payment of in-place CCS that does not rely on the Gaussian distribution and allows a variety of pay factors around the target mean. A new approach was developed, called the percent-within-distribution (PWD), which calculates a quality measure from a 28-day CCS sample by comparing the sample to any type of design distribution using a Bayes process. Random variables were used to guide the new approach and the simulated responses that the industry might take. We showed how the new quality measure can be used for acceptance and payment under a double-bounded pay factor schedule, but also how it could be used to design a pay factor schedule in the absence of complete lifecycle cost data. The research team also created a decision-support tool to manage the implementation of the new approach. The tool allows the user to specify and visualize their design distribution, then calculate the PWD from a sample. The tool is based in MS Excel so that it will be useful to a variety of DOT QA/QC personnel.
• Format:
  PDF
• Funding:
  69A3551847101
• Collection(s):
  University Transportation Centers
• Main Document Checksum:
  urn:sha-512:6f317d6bf8b8c724324bef84af15cc206bb2cb9d33c4df16e5b9f3d4c41892bdd597ca69e83f18fd180d95cc92736e35a6a25f6fc8470736ee20423ff7ec33ae
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/88971/dot_88971_DS1.pdf
• File Type:
  [PDF - 968.10 KB ]